1. Field
The invention concerns a fire extinguishing system for an airplane, in particular, for firefighting in cargo holds of the airplane, comprising at least one extinguishing agent storage unit with an activatable closing device, which makes possible, when activated, the flowing out of the extinguishing agent from the extinguishing agent storage unit, and a supply line, connected with the closing device and at least one outlet opening, by means of which the extinguishing agent can be conducted from the extinguishing agent storage unit to the outlet opening, so as to eject it there, in a targeted manner, into a relevant space for firefighting. In addition, the invention concerns a method for fighting fires in an airplane.
2. Brief Discussion of Related Art
Airplanes beyond a certain weight class must, as is known, have a fire protection system. This fire protection system consists of a fire alarm system and a fire extinguishing system. The fire alarm system typically includes a fire sensor or over-temperature sensor, which must be installed in every particularly fire-prone area of the airplane, monitoring devices and heat devices in the cockpit. Particularly fire-prone areas are: the engines and auxiliary power systems, such as the auxiliary turbines (APU, Auxiliary Power Unit). Moreover, fire and over-temperature sensors can be installed in the following areas: landing gear shafts, cargo holds and areas which lead to hot engine air (“bleed air”) for the deicing or heating. Each response to a fire alarm system triggers an optical and usually also an acoustic warning in the cockpit. In particular, cargo holds of the classes B, C, and E must be included in the fire alarm system. Fire is predominantly not detected there by a temperature measurement, but rather by smoke detectors and/or gas detectors because of the large volume of the cargo holds.
In all areas in the airplane in which a hazard for the airplane and its crew can appear due to a fire, a fire extinguishing means must be available. A fire can be fought using a manual fire extinguisher in the cockpit and the passenger cabin. Permanently installed fire extinguishing systems must be available at inaccessible places, especially in the cargo holds, on the engines, and the auxiliary power systems. For these permanently installed fire extinguishing systems, the cockpit crew must make the decision to use an extinguisher when the fire alarm system signals a fire alarm for one of these areas.
The permanently installed fire extinguishing systems comprise at least one extinguishing agent storage unit with a closing device located on it. The extinguishing agent storage unit is connected with one or more supply lines via the closing device; through the lines, the extinguishing agent gets from the extinguishing agent storage unit to the exit openings located in fire hazard areas, so as to be ejected, in a targeted manner, from there for fighting fire in predetermined fire hazard areas. The closing device is activated by the cockpit crew by means of a manually actuatable input element, namely a toggle or key, which is protected from an unintended actuation. The closing device can, for example, be formed as diaphragms, which can be pyrotechnically activated once by means of an electrical ignition impulse—that is, once to open and cannot be closed again. By the actuation of the input element, the ignition impulse is initiated, which leads to the bursting of the diaphragms.
A number of fire extinguishing systems are known for airplanes. Thus, a fire extinguishing device with two fire extinguishing agent containers for extinguishing agents under excess pressure to produce a first and second fire extinguishing deployment for cargo holds of airplanes can be found in DE 36 15 415 C2. DE 10 051 662 A1 reveals a device in which the oxygen required for the maintenance of the fire is removed by the introduction of nitrogen into the closed space, and thus the fire is extinguished. EP 0 234 056 A1 describes a fire extinguishing system to extinguish a fire which has erupted within the cabin or a cargo hold of a passenger airplane. This fire extinguishing system contains a reservoir to store pressure-liquefied halon, which is connected, via a pipeline system, to extinguishing nozzles, located within the cabin or the cargo hold. The halon is supplied to the cabin or the cargo hold as an extinguishing agent, building up the extinguishing-effective concentration in a short time, via outlet openings (extinguishing nozzles).
Nowadays, there is a decreasing tendency to use halons as extinguishing agents. Halons are halogenated hydrocarbons, the basic molecules which consist of carbon and hydrogen and in which a variable number of hydrogen atoms is replaced by halogen atoms. The presence of fluorine brings about a great stability of the molecules and thus contributes decisively to these compounds being comparatively nontoxic. The extinguishing effect of the halons is based on the fact that they decompose in flame heat and cleavage products, reacting with the carriers of the combustion reaction. In this way, the combustion reaction is stopped. This process is designated as the anticatalytic effect.
Nowadays, the halons trifluorobromomethane (CF3Br, BTM, halon 1301) and bromochlorodifluoromethane (CBrClF2, BCF, halon 1211) are still most frequently used in airplanes. They have an excellent extinguishing effect and are comparatively nontoxic. The decomposition products formed during the extinguishing deployment, however, are toxic, but in contrast to the CO2 gas and the carbon monoxide (CO) formed during the fire, have a warning effect due to the irritation of the mucosa. Halons, however, as is known, are also climate-affecting substances, which, on the one hand, degrade the ozone layer of the stratosphere, and, on the other hand, promote the greenhouse effect. Therefore, they are forbidden by the Montreal Protocol (1989). For deployment as an extinguishing agent in airplane extinguishing systems, however, limited special exemptions exist.
Already, effective alternative extinguishing agents exist that contribute less, or not at all, toward increasing the greenhouse effect, and have smaller effect on the ozone, to none at all, in the stratosphere, for example, trifluoroiodomethane (CF3I). In the meantime, these alternative extinguishing agents are available at lower costs in comparison to the halons 1301 and 1211. The alternative extinguishing agents are, however, not suitable for spaces occupied by persons because they are harmful/toxic to humans. Since cargo holds are counted among the person-occupied spaces of an airplane, because at least on the ground, persons may stay in the cargo holds during the loading and unloading of the cargo holds, these alternative extinguishing agents are not used, at present, in extinguishing agent systems for cargo holds. Therefore, in addition to the basic need for an extinguishing agent that is not harmful to humans and the environment, as a replacement for the hitherto still used halons 1211 and 1301, there is a need, because of economic considerations, to use, as extinguishing agents in fire extinguishing systems for cargo holds, the more favorable extinguishing agents that are already available nowadays, but that have not been approved for use in cargo holds. As a result of the large volume of the cargo holds, a correspondingly large quantity of extinguishing agent is needed in the extinguishing agent storage units of the fire extinguishing systems, which with a use of the alternative extinguishing agents, generates lower costs in comparison to the halons 1211 and 1301.
Another disadvantageous aspect of the known fire extinguishing systems comes from the fact that the fire alarm system and the fire extinguishing system of an airplane are always completely deployable when the airplane is provided with power, that is, in the state “Electrical Power ON”. This electrical state is also frequently present when the airplane is on the ground and the engines are turned off, for example, if work is being done on the airplane for maintenance purposes, or for loading and unloading cargo, for catering, or for cleaning the cabin in the turned-off or parked position. In individual cases, it happens that the manual input element for the triggering of a fire extinguishing system by maintenance personnel or the crew is actuated inadvertently and/or unintentionally without a fire having been reported. Furthermore, within the scope of system tests, false alarms of the fire alarm system can be generated, that is, there is a fire alarm in the cockpit without there actually being a fire. The disadvantage is that in these cases, the closing device on the extinguishing agent storage unit is activated as a result of a manual actuation of the input element, and as a result, the extinguishing agent is ejected via the outlet openings of the individual fire extinguishing system without there actually being a fire to be extinguished.
In addition, with a fire actually present in the cargo hold of a plane parked on the ground, the extinguishing agent concentration required for an effective fighting of the fire is not attained in the case of an opened cargo hold door of the cargo hold, after an activation of the fire extinguishing system, so that such a fire cannot be extinguished with a permanently installed fire extinguishing system, or at least cannot be done so effectively, but rather, it becomes necessary to resort to mobile ground extinguishing systems (fire department, manual fire extinguishers, etc.). In all of these cases, extinguishing agents have been introduced, up to now, with ground operation of the airplane, intentionally or unintentionally, without this extinguishing agent being able to act effectively, either because there is no fire at all or because the cargo hold door or another door of an affected space is open and a sufficient fire extinguishing effect is not attainable due to the then possible air exchange with the ambient air in the case of a fire which actually exists.
In particular, the possibility of a triggering of the fire extinguishing system for a cargo hold in which, perhaps, persons may be present, also poses the requirement that, at present, the only extinguishing agents that may be used for cargo holds are those which are permissible for spaces occupied by persons. As was stated before, at present, the more favorable alternative extinguishing agents cannot be used for cargo holds.